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alkali metals

...can be made by passing oxygen through a liquid-ammonia solution of the alkali metal, although sodium peroxide is made commercially by oxidation of sodium monoxide with oxygen. Sodium
superoxide (NaO
2) can be prepared with high oxygen pressures, whereas the
superoxides of rubidium, potassium, and cesium can be prepared directly by combustion in air. By contrast, no...

In the
superoxide ion, O
2−, the oxygen has an oxidation number of −
1/2. The stability of metal
superoxides depends on the size and the electropositive character of the metal. The larger the metal and the more electropositive it is, the greater the stability of its
superoxide. Thus, potassium (K), rubidium (Rb), cesium (Cs),...